Specialize in order to unroll intermediate doesn't work with multiple outputs

[abadams]

This schedule really ought to work:

#include "Halide.h"

using namespace Halide;

int main(int argc, char **argv) {
    Func intermediate("intermediate");

    Func output1("output1"), output2("output2");

    Var x("x"), y("y"), c("c");

    intermediate(x, y, c) = x + y + c;

    output1(x, y, c) = intermediate(x, y, c);
    output2(x, y, c) = intermediate(x, y, c);

    intermediate.compute_root()
        .specialize(
            output1.output_buffer().dim(2).extent() == 3 &&
            output1.output_buffer().dim(2).min() == 0 &&
            output2.output_buffer().dim(2).extent() == 3 &&
            output2.output_buffer().dim(2).min() == 0)
        .unroll(c);

    // Works
    output1.compile_jit();

    // Fails with:

    // Can only unroll for loops over a constant extent.
    // Loop over intermediate.s0.c has extent (max(output1.extent.2 + output1.min.2, output2.extent.2 + output2.min.2) - min(output1.min.2, output2.min.2)).

    Pipeline p{{output1, output2}};
    p.compile_jit();

    return 0;
}

[abadams]

Works if you explicit tell Halide the outputs have the same size in that dimension:

    output1.output_buffer().dim(2).set_bounds(output2.output_buffer().dim(2).min(),
                                              output2.output_buffer().dim(2).extent());

[abadams]

Alternatively:

intermediate.bound(c, 0, output1.output_buffer().dim(2).extent());

Still.. the original ought to work.